Red Sea"s Nitrate Pro Test Kit is an advanced colorimetric test with comparator, measuring the level of nitrate in your reef aquarium to an exceptionally high accuracy of 0.12ppm NO3.This test kit, when used in conjunction with the Phosphate Pro Kit, enables accurate dosing of Red Sea"s NO3: PO4- X (biological nitrate and phosphate reducer) which is part of the complete Red Sea Reef Care Program.